Recently, as the Internet is more widely used, the amount of contents supplied by traditional content distributors including Internet portals or Internet service providers is on increase. In addition, Internet use sharply increases in an active form in which users themselves create and provide contents rather than a passive form in which getting information from such traditional content distributors is only focused.
In other words, the contents including web documents, news articles, images, videos and media information were mainly provided only by online portals etc. in the past but recently such contents are actively produced and distributed by individual users. By the increase in the production and distribution of user created content (UCC) and web hosting services such as blogs or websites capable of providing several functions to enable more users to conveniently create content, the situation is deepening.
Such user created content is created with the procedure of transmitting files such as images or videos recorded in a terminal of a user to the servers of blog or webpage service providers (shortly, service servers) or the procedure of suggesting a link to the already existing files on a network at the same time with the procedure which allows the user to prepare data in a text form.
The exchange of various types of contents through the Internet enables users to share information, but some users may share obscene content such as adult videos, adult photos and adult comics and illegal ads through the Internet which results in bad spillover effects even to many fair users.
To block such an obscene content, a variety of methods have been proposed from the past, which, for example, include a scheme for blocking an Internet search engine from a lewd content in order to prevent the users from accessing such a content; a scheme for deleting an obscene content by a service server when such a content is uploaded and reported by a user; or a scheme for checking how much percentage the skin color is occupied in an image or a video file and blocking the obscene content when the percentage is high.